1 /*
2 * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 #include "cds/cdsEnumKlass.hpp"
26 #include "cds/heapShared.inline.hpp"
27 #include "classfile/systemDictionaryShared.hpp"
28 #include "classfile/vmClasses.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "oops/fieldStreams.inline.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/fieldDescriptor.inline.hpp"
33
34 #if INCLUDE_CDS_JAVA_HEAP
35
36 bool CDSEnumKlass::is_enum_obj(oop orig_obj) {
37 Klass* k = orig_obj->klass();
38 return k->is_instance_klass() &&
39 InstanceKlass::cast(k)->is_enum_subclass();
40 }
41
42 // !!! This is legacy support for enum classes before JEP 483. This file is not used when
43 // !!! CDSConfig::is_dumping_aot_linked_classes()==true.
44 //
45 // Java Enum classes have synthetic <clinit> methods that look like this
46 // enum MyEnum {FOO, BAR}
47 // MyEnum::<clinint> {
48 // /*static final MyEnum*/ MyEnum::FOO = new MyEnum("FOO");
49 // /*static final MyEnum*/ MyEnum::BAR = new MyEnum("BAR");
50 // }
51 //
52 // If MyEnum::FOO object is referenced by any of the archived subgraphs, we must
53 // ensure the archived value equals (in object address) to the runtime value of
54 // MyEnum::FOO.
55 //
56 // However, since MyEnum::<clinint> is synthetically generated by javac, there's
57 // no way of programmatically handling this inside the Java code (as you would handle
58 // ModuleLayer::EMPTY_LAYER, for example).
59 //
60 // Instead, we archive all static field of such Enum classes. At runtime,
61 // HeapShared::initialize_enum_klass() skips the <clinit> method and instead pulls
62 // the static fields out of the archived heap.
63 void CDSEnumKlass::handle_enum_obj(int level,
64 KlassSubGraphInfo* subgraph_info,
65 oop orig_obj) {
66 assert(!CDSConfig::is_dumping_aot_linked_classes(), "only for legacy support of enums");
67 assert(level > 1, "must never be called at the first (outermost) level");
68 assert(is_enum_obj(orig_obj), "must be");
69
70 InstanceKlass* ik = InstanceKlass::cast(orig_obj->klass());
71 if (ik->has_archived_enum_objs()) {
72 return;
73 }
74
75 ik->set_has_archived_enum_objs();
76
77 oop mirror = ik->java_mirror();
78 for (JavaFieldStream fs(ik); !fs.done(); fs.next()) {
79 if (fs.access_flags().is_static()) {
80 archive_static_field(level, subgraph_info, ik, mirror, fs);
81 }
82 }
83 }
84
85 void CDSEnumKlass::archive_static_field(int level, KlassSubGraphInfo* subgraph_info,
86 InstanceKlass* ik, oop mirror, JavaFieldStream& fs) {
87 ResourceMark rm;
88 fieldDescriptor& fd = fs.field_descriptor();
89 if (fd.field_type() != T_OBJECT && fd.field_type() != T_ARRAY) {
90 guarantee(false, "static field %s::%s must be T_OBJECT or T_ARRAY",
91 ik->external_name(), fd.name()->as_C_string());
92 }
93 oop oop_field = mirror->obj_field(fd.offset());
94 // There should be no oops for ObjArrayKlass but InstanceKlass::array_klasses holds a list of ObjArrayKlass,
95 // therefore we need the super of the refined array klass.
96 Klass* oop_field_klass = oop_field->is_refined_objArray() ? oop_field->klass()->super() : oop_field->klass();
97 if (oop_field == nullptr) {
98 guarantee(false, "static field %s::%s must not be null",
99 ik->external_name(), fd.name()->as_C_string());
100 } else if (oop_field_klass != ik && oop_field_klass != ik->array_klass_or_null()) {
101 guarantee(false, "static field %s::%s is of the wrong type",
102 ik->external_name(), fd.name()->as_C_string());
103 }
104 bool success = HeapShared::archive_reachable_objects_from(level, subgraph_info, oop_field);
105 assert(success, "VM should have exited with unarchivable objects for _level > 1");
106 int root_index = HeapShared::append_root(oop_field);
107 log_info(aot, heap)("Archived enum obj @%d %s::%s (" INTPTR_FORMAT ")",
108 root_index, ik->external_name(), fd.name()->as_C_string(),
109 p2i((oopDesc*)oop_field));
110 SystemDictionaryShared::add_enum_klass_static_field(ik, root_index);
111 }
112
113 bool CDSEnumKlass::initialize_enum_klass(InstanceKlass* k, TRAPS) {
114 if (!HeapShared::is_archived_heap_in_use()) {
115 return false;
116 }
117
118 RunTimeClassInfo* info = RunTimeClassInfo::get_for(k);
119 assert(info != nullptr, "sanity");
120
121 if (log_is_enabled(Info, aot, heap)) {
122 ResourceMark rm;
123 log_info(aot, heap)("Initializing Enum class: %s", k->external_name());
124 }
125
126 int i = 0;
127 for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
128 if (fs.access_flags().is_static()) {
129 int root_index = info->enum_klass_static_field_root_index_at(i++);
130 fieldDescriptor& fd = fs.field_descriptor();
131 assert(fd.field_type() == T_OBJECT || fd.field_type() == T_ARRAY, "must be");
132 oop root_object = HeapShared::get_root(root_index, /*clear=*/true);
133 k->java_mirror()->obj_field_put(fd.offset(), root_object);
134 }
135 }
136 return true;
137 }
138 #endif // INCLUDE_CDS_JAVA_HEAP